Heat detector casing



FIG. 1 is a perspective view of the side elevation of the casing, particularly showing the inventive design thereof;

FIG. 2 is a bottom view thereof;

FIG. 3 is a top view thereof;

FIG. 4 is a front view thereof;

FIG. 5 is a rear view thereof;

FIG. 6 is a right view thereof; and,

FIG. 7 is a left view thereof. 

The ornamental design for a heat detector casing, as shown and described. 